In optical communications systems, conventional intensity modulation creates an optical spectrum that is mirror-imaged about the central carrier wavelength. The spectrum on either side of the carrier wavelength is mutually redundant, since only one side is actually needed to convey data. Therefore, these typical approaches use about twice the bandwidth that is actually required. Vestigial sideband (VSB) transmission is a known technique for reducing bandwidth and power requirements. However, prior VSB solutions have been hampered by their inability to control the wavelengths of the optical carriers with sufficient accuracy relative to the optical filters utilized in optical communications systems. Furthermore, the typical VSB implementations have been hampered by their complexity and associated cost.
Therefore a need exits for an improved vestigial sideband transmitter/receiver to dynamically control the wavelengths of the optical signals relative to the optical filters needed to suppress the unwanted sidebands. Furthermore, the bandwidth reduction afforded by the improved vestigial sideband transmitter/receiver is required to avoid problems associated with chromatic dispersion. This is particularly important for data rates of 10 Gb/s, 40 Gb/s, and higher. Furthermore, the bandwidth reduction afforded by the improved vestigial sideband transmitter/receiver is needed to improve the optical amplifier's ability to effectively boost the power of the aggregated VSB signals for transmission over long distances. Furthermore, an improved vestigial sideband transmitter/receiver is needed to provide an economical and practical increase in the data capacity of fiber optic transmission systems.